Methods for promoting intrinsic activation in single chamber implantable cardiac pacing systems

Abstract

Cardiac pacing methods for an implantable single chamber pacing system, establish an offset rate for pacing at a predetermined decrement from either a baseline rate (i.e. dictated by a rate response sensor), or an intrinsic rate. Pacing maintains the offset rate until x of y successive events are paced events, at which time the offset rate is switched to the baseline rate for pacing over a predetermined period of time. Following the period, if an intrinsic event is not immediately detected, within the interval of the offset rate, the rate is switched back to baseline for pacing over an increased period of time. Some methods establish a preference rate, between the offset and baseline rates, wherein an additional criterion, for switching from the offset rate to the baseline rate, is established with respect to the preference rate.

We claim: 
     
       1. A method for rate adaptive cardiac pacing that employs implanted electrodes for single chamber pacing and sensing, and the method comprising the steps of:
 establishing a baseline rate for pacing stimulation; 
 establishing an offset rate for pacing stimulation, the offset rate being lower than the baseline rate; 
 sensing for intrinsic events by means of the implanted electrodes; 
 applying a pacing stimulation pulse by means of the implanted electrodes to maintain the offset rate; 
 establishing a preference rate that falls between the baseline rate and the offset rate; and 
 switching from the offset rate to the baseline rate and pacing at the baseline rate in response to intrinsic events meeting a criterion with respect to the preference rate, the criterion being one of: x of y successive intrinsic events falling below the preference rate, x being greater than one and y being greater than or equal to x; and a measure of central tendency of the rates of successive intrinsic events falling below the preference rate. 
 
     
     
       2. The method of  claim 1 , wherein the preference rate is established according to a predetermined decrement of the baseline rate, the predetermined decrement being one or a combination of: a fixed beats per minute decrement, a percentage beats per minute decrement, a fixed interval increment, and a percentage interval increment. 
     
     
       3. The method of  claim 1 , further comprising applying at least one pacing stimulation pulse at a rate between the preference rate and the baseline rate, in response to the intrinsic events meeting the criterion with respect to the preference rate, and prior to the corresponding switch to the baseline rate. 
     
     
       4. The method of  claim 1 , further comprising applying at least one pacing stimulation pulse at a rate between the offset rate and the baseline rate prior to the switch to the baseline rate. 
     
     
       5. The method of  claim 1 , wherein the baseline rate for pacing stimulation is established according to input from one or more rate response sensors. 
     
     
       6. A single chamber cardiac pacing system configured to be wholly implanted against an endocardial or epicardial surface, the system including a pulse generator having one or more rate response sensors and a microprocessor element being preprogrammed to direct the pulse generator to execute a method comprising the following steps:
 establishing a baseline rate for pacing stimulation; 
 establishing an offset rate for pacing stimulation, the offset rate being lower than the baseline rate; 
 sensing for intrinsic events by means of the implanted electrodes; 
 applying a pacing stimulation pulse by means of the implanted electrodes to maintain the offset rate; 
 establishing a preference rate that falls between the baseline rate and the offset rate; and 
 switching from the offset rate to the baseline rate and pacing at the baseline rate in response to intrinsic events meeting a criterion with respect to the preference rate, the criterion being one of: x of y successive intrinsic events falling below the preference rate, x being greater than one and y being greater than or equal to x; and a measure of central tendency of the rates of successive intrinsic events falling below the preference rate. 
 
     
     
       7. The system of  claim 6 , wherein the preference rate is established according to a predetermined decrement of the baseline rate, the predetermined decrement being one or a combination of: a fixed beats per minute decrement, a percentage beats per minute decrement, a fixed interval increment, and a percentage interval increment. 
     
     
       8. The system of  claim 6 , wherein the microprocessor element is further preprogrammed to direct the pulse generator to execute the following additional step:
 applying at least one pacing stimulation pulse at a rate between the preference rate and the baseline rate, in response to the intrinsic events meeting the criterion with respect to the preference rate, and prior to the corresponding switch to the baseline rate. 
 
     
     
       9. The system of  claim 6 , wherein the microprocessor element is further preprogrammed to direct the pulse generator to execute the following additional step:
 applying at least one pacing stimulation pulse at a rate between the offset rate and the baseline rate prior to the switch to the baseline rate. 
 
     
     
       10. The method of  claim 6 , wherein the baseline rate for pacing stimulation is established according to input from one or more rate response sensors.